On Fri, Oct 11, 2024 at 8:21 AM Andrei Lepikhov <lepihov@gmail.com> wrote:
On 10/10/24 23:51, Robert Haas wrote: > On Wed, Sep 18, 2024 at 11:48 AM Robert Haas <robertmhaas@gmail.com> wrote: > 1. If you want to specify in-query hints using comments, how does your > extension get access to the comments? Having designed two features [1,2] that do the stuff mostly similar to pg_hint_plan but based on real cardinalities earned from previous executions, I can say the most annoying problem is hinting subqueries & CTEs. Sometimes, you want to hint at the top query and not touch the subquery and vice versa. Sometimes, users get stuck in accidents when a flattened subquery influences your hint. So, the key property to invent in advance should be an identification system. I have chosen hash-based identification when each RelOptInfo has a hash created over values of relids, restrictions and hashes of underlying RelOptInfos. At the core, it seems inappropriate.
out of curiosity, why do You think it would be inappropriate to do so in the core? Maybe it Is something similiar to compute_query_id that can be computed externally too. I remember Tom arguing that query_id should be computed externally by extension for some reasons because each extension may want differently to fingerprint the queries, but I cannot find link to discussion now or bring more details)
